Vanadium is used in various applications. The main application thereof at present is its addition to steel. The addition of vanadium to steel in the form of ferrovanadium improves the mechanical properties and heat resistance of steel. Vanadium is also used as a catalyst and as an electrolyte of redox flow batteries.
Vanadium is obtained in the form of vanadium pentoxide (V2O5) by roasting and extraction of vanadium slag. However, vanadium pentoxide obtained by this method is expensive. Consequently, the use of vanadium pentoxide in the electrolyte of redox flow batteries and the like leads to higher prices for redox flow batteries.
Attention has recently been focused on vanadium contained in incineration ash generated following combustion of fuel in boilers such as those used at power plants. Incineration ash ends up becoming industrial waste depending on the ash and components contained therein. It if were possible to recover vanadium from this incineration ash, it would enable vanadium compounds to be acquired at low cost.
For example, Non-Patent Document 1 describes that a sulfuric acid solution is superior to an aqueous ammonia solution as a solvent for leaching vanadium ions from burning ash. In addition, Patent Document 1 describes a method for obtaining a trivalent vanadium salt by reacting inorganic acid with a trivalent vanadium compound obtained by calcination of precipitator ash. In addition, Patent Document 2, for example, describes a method for obtaining vanadium compounds by leaching vanadium ions from Orimulsion ash in a solvent at pH 3 or lower and solvent extraction.